EP2694714A2

EP2694714A2 - Air supply unit and method for applying an air supply unit

Info

Publication number: EP2694714A2
Application number: EP12707622.2A
Authority: EP
Inventors: Jozef Peeters
Original assignee: Picanol NV
Current assignee: Picanol NV
Priority date: 2011-04-06
Filing date: 2012-03-09
Publication date: 2014-02-12
Anticipated expiration: 2032-03-09
Also published as: WO2012136442A3; TR201906408T4; BE1019803A3; CN103547722B; EP2694714B1; WO2012136442A2; CN103547722A

Abstract

The invention relates to an air supply unit (1) for supplying air to a blowing device (3) of an airjet weaving machine with a main body (2) comprising a main duct (4) for supplying air at a first pressure from an inlet (7) to an outlet (8), a secondary duct (9) for supplying air at a second pressure from an inlet (13) to the outlet (8), with a first air flow control valve (14) provided in the main duct (4) and with a second air flow control valve (20) provided in the secondary duct (9), wherein the secondary duct (9) ends in the main duct (4) downstream of the first air flow control valve (14) and wherein a non-return valve (21) is provided in the secondary duct (9) downstream of the second air flow control valve (20). The invention further relates to a method for applying an air supply unit (1).

Description

Air supply unit and method for applying an air supply unit-

Description

Technical Field

The invention relates to an air supply unit with a main body comprising at least one inlet connectable to a compressed air source, an outlet connectable to a blowing device, a main duct for supplying air at a first pressure from the at least one inlet to the outlet, a secondary duct for supplying air at a second pressure from the at least one inlet to the outlet, with a first air flow control valve provided in the main duct and arranged to control the supply of compressed air through the main duct to the outlet, and with a second air flow control valve provided in the secondary duct, wherein the second air flow control valve is a throttle valve and arranged to throttle compressed air in the secondary duct.

Prior Art

US 6,062,273 discloses an apparatus for supplying compressed air to a main blowing device of an airjet weaving machine for weft thread insertions with an integrated air supply unit including an inlet opening or inlet directly connected to the compressed air supply, an outlet connected to the main blowing device and air flow control valves with valve drives. Main ducts and bypass ducts provide communication between the inlet and the outlet with the airflow control valves controlling the supply of air to the outlet of the air supply unit. The air flow con- trol valves include a shut-off valve arranged to control in an on/off manner the supply of compressed air from the main duct to the outlet; a first adjustable throttling valve arranged to throttle compressed air supplied to the outlet during weft thread insertions when the shut-off valve is open and a second adjustable throttling valve arranged to throttle compressed air supplied to the outlet be- tween weft thread insertions when the shut-off valve is closed.

US 6,305,433 discloses an air supply unit with a main body or air supply block with a substantially straight parallelepiped housing. The air supply block includes ducts and switched and/or adjusted valves driven by valve drives ar- ranged between inlets and outlets. The air supply block provides two outlets at one longitudinal side of the housing, each outlet being associated with its own valves. Three sides of the housing are free of valve drives or other elements for allowing several blocks to be connected to each other via these sides.

It is known from US 5,970,996 to provide a pneumatic system, wherein two main blowing devices are each connected by a first branch to a compressed-air source supplying high-pressure compressed air for purposes of weft thread insertion. The main valve is opened by a control unit to insert a weft thread and thereafter is closed again. Each of the main blowing devices is connected through a secondary branch to the compressed-air source to supply low- pressure compressed air to the main blowing devices. The two secondary branches comprise a common pressure regulator and one throttling valve each. A control unit is provided for adjusting the throttling valve to different throttling gaps. The control unit may adjust the throttling valve so that, immediately after closing the main valve compressed air of higher pressure shall be supplied through the secondary branch, the pressure of the compressed air thereafter being reduced by adjusting the throttling valve. The pressure then will be raised again in timely manner before the next insertion of a weft thread. A non-return valve may be provided in each secondary branch downstream of the throttling valve for precluding the pressure, when released by the main valve, from enter- ing the secondary branch. After closing the main valve the pressure at the blowing devices will drop only very slowly. This effect is further assisted as a length of a pneumatic line between the throttling valve and the non-return valve is comparatively long and an air volume of the compressed air in the secondary duct before opening the non-return valve is high.

Summary of the Invention

It is the object of the invention to provide an air supply unit for supplying air to a blowing device of an airjet weaving machine and a method for applying an air supply unit for supplying air to a blowing device of an airjet weaving machine, wherein a fast and reliable transition from an air supply at a first pressure to an air supply at a second pressure and vice versa is achieved.

This object is solved by an air supply unit for supplying air to a blowing device of an airjet weaving machine and a method for applying an air supply unit for supplying air to a blowing device of an airjet weaving machine with the features of claims 1 and 15. Preferred embodiments are defined in the dependent claims. It is the basic idea of the invention to provide an air supply unit for supplying air to a blowing device of an airjet weaving machine with a main body comprising at least one inlet connectable to a compressed air source, an outlet connectable to the blowing device, a main duct for supplying air at a first pressure from the at least one inlet to the outlet, a secondary duct for supplying air at a second pressure from the at least one inlet to the outlet, with a first air flow control valve provided in the main duct and arranged to control the supply of compressed air through the main duct to the outlet, and with a second air flow control valve pro- vided in the secondary duct, wherein the second air flow control valve is a throttle valve and arranged to throttle air in the secondary duct, wherein the secondary duct ends into the main duct downstream of the first air flow control valve, and wherein a non-return valve is provided in the secondary duct downstream of the second air flow control valve. The main duct is also named the first duct. The non-return valve is arranged in the secondary duct near to the place where the secondary duct ends into the main duct.

Generally, the first pressure, also referred to as weaving pressure, is sufficiently high for allowing a weft thread insertion. Appropriate first air pressures are for example in the range of about 2 bar to about 7 bar. The second pressure, also referred to as holding pressure, is generally lower than the first pressure. Using a second pressure in the range of about 0,1 bar has been successful for reliably holding a weft thread in the blowing device when the weft thread not inserted. The non-return valve opens or closes due to pressure differences upstream and downstream of the non-return valve. No actuator is required for the non-return valve. By providing the non-return valve downstream of the second air flow control valve in the secondary duct of a main body, a compact structure of the air supply unit is given, wherein an air volume between the non-return valve and the second air flow control valve and/or between the non-return valve and the first air flow control valve may be kept small. This allows prevailing pressures upstream or downstream of the non-return valve to be quickly adapted to changes in the conditions due to an opening or closing of the first air flow control valve and a subsequent closing or opening of the non-return valve. Thereby, the non-return valve opens or closes quickly in response to a closing or opening of the first air flow control valve for a fast and reliable transition from an air supply at a first pressure to an air supply at a second pressure and vice versa. The object is also solved by a method for applying an air supply unit for supplying air to a blowing device of an airjet weaving machine for inserting a weft thread, wherein the air supply unit comprises a main body, the main body com- prises at least one inlet connected to a compressed air source, an outlet connected to the blowing device, a main duct for supplying air at a first pressure from the at least one inlet to the outlet, a secondary duct for supplying air at a second pressure from the at least one inlet to the outlet, wherein the air supply unit further comprises a first air flow control valve provided in the main duct and arranged to control the supply of compressed air through the main duct to the outlet and a second air flow control valve provided in the secondary duct, wherein the second air flow control valve is a throttle valve and arranged to throttle air in the secondary duct, wherein the secondary duct ends into the main duct downstream of the first air flow control valve, and wherein a non- return valve is provided in the secondary duct downstream of the second air flow control valve, wherein the method comprising the following steps of: supplying air at a second pressure via the secondary duct while the first air flow control valve is closed, opening the first control valve and supplying air at a first pressure via the main duct for a weft thread insertion of a weft thread, wherein the first pressure is higher than the second pressure, and subsequently closing the first air control valve.

When closing the first air flow control valve, the pressure in the main duct downstream of the first air flow control valve will drop. When the pressure at the outlet is below a pressure in the secondary duct upstream of the non-return valve, the non-return valve opens and air is supplied at the second pressure. While no air flow is present through the second air flow control valve, the second air flow control valve has no throttling effect and the pressure upstream and downstream of the second air flow control is essentially equal. Therefore, a higher pressure will act on the non-return valve for opening the non-return valve than after the non-return valve has opened and air flows through the second air flow control valve. Therefore, a fast opening of the non-return valve is achieved. For example, the pressure prevailing before the opening of the non-return valve may be chosen to 1 .5 bar, whereas the pressure supplied via the secondary duct after the non-return valve has opened is throttled to 0,1 bar. Due to the fast opening of the non-return valve and the small volumes of the secondary duct, a pressure drop at the outlet to a pressure below the desirable holding pressure is successfully avoided.

According to an embodiment, an essentially linear passageway is provided in the main body for the formation of the secondary duct, wherein the second air flow control valve and the non-return valve are arranged in line in the passageway. Preferably, essentially linear passageways are provided in the main body for the formation of both the main duct and the secondary duct. The passageways are manufactured for example as boreholes. For a simple manufacturing, the passageways extend preferably at least partially in parallel. The volume of the secondary duct downstream of the second air flow control valve is preferably minimized. The volume is kept sufficiently large to meet constraints of design and mechanical strength of the valves provided in the duct and the value of the second pressure. In one embodiment, the respective passageway is formed in the main body for the secondary duct, wherein tubular or sleeve-type elements are provided in order to minimize the air volume in the secondary duct.

After closing the first air flow control valve, it is advantageous that the pressure downstream of the first air flow control valve drops rapidly. By minimising the volume of air downstream of the first air flow control valve, in particularly by closing the non-return valve arranged between the main duct and the secondary duct, a fast dropping of the pressure is achieved after closing the first air flow control valve. This allows to define precisely the moment at which a main blowing device is no longer blowing on the weft thread at the end of the weft thread insertion, what prevents too much blowing on a weft thread which is braked or already halted, so that a damaging of the weft thread is avoided. This is advantageous to brake and/or hold a weft thread as desired at the end of the weft thread insertion. In another embodiment the valve seat of the second air flow control valve is mounted on or formed integrally with an inlet of the non-return valve. In preferred embodiments, a sleeve-type element with a central through-opening is provided in a passageway of the main body, wherein the central through- opening functions as the inlet of the non-return valve and the valve seat of the second air flow control valve is provided in the entry region of central through- opening at a first face of the sleeve-type element. According to an embodiment the sleeve-type elements with a central through-opening are provided in a pas- sageway of the main body, wherein the non-return valve is arranged between the sleeve-type elements and wherein a valve seat of the second air flow control valve is provided at the entry region of central through-opening at the sleeve-type element arranged upstream of the other sleeve-type element. The passageway, in particular a borehole, may be dimensioned sufficiently large for allowing a simple manufacturing of the main body. The diameter of the through- opening may be chosen to be substantially smaller than the diameter of the passageway provided in the main body in order to minimize the volume of the secondary duct. In addition, the conjoint embodiment of the valve seat and the inlet of the non-return valve as a sleeve-type element allows for a compact design.

Preferably, the sleeve-type element is fixedly secured in the secondary duct, in particular via a screw connection. The sleeve-type element may easily be re- placed. For example in order to alter a throttling action of the second air flow control valve or to provide another non-return valve.

In one embodiment, the second air flow control valve comprises a stationary valve seat with an essentially circular-cylindrical inside surface and a plunger with a conical outer surface. The conicity of the plunger preferably is between 3 ° and 30 °. In a preferred embodiment, the position of the plunger is adjustable with respect to the valve seat for adjusting a throttling gap.

In another embodiment, the second air flow control valve comprises an actuator for adjusting the throttling gap, in particular an electrically controlled actuator. The actuator preferably is coupled with a screw-thread device for transforming a rotational movement of the actuator into an axial movement of the plunger having a conical outer surface. The second air flow control valve can be set to a desired throttling gap.

In one embodiment, the plunger for example is guided upon movement by sidewalls of the passageway. According to still another embodiment, the second air flow control valve comprises a support structure sealingly arranged in the secondary duct, wherein the plunger, in particular a plunger skirt, is slideably supported in the support structure. The non-return valve, the second air flow control valve, the support structure and the actuator for the second air flow control valve are inserted in the passageway formed in the main body. The support structure is sealingly arranged in the passageway in order to avoid air losses. In one embodiment, the plunger comprises a plunger skirt and a plunger head, which are secured to each other to form a uniform element. In other embodiments, the plunger skirt and the plunger head are formed integrally. With inte- gral is meant self existing. The support structure allows dimensioning the diameter of the plunger smaller than the diameter of the passageway of the main body.

In a preferred embodiment, a diameter of the plunger is smaller than a cross- section of the second duct part of the secondary duct upstream of the valve seat of the second air flow control valve. This allows to minimize the force required for moving the plunger.

In another embodiment, the first air flow control valve is a shut-off valve ar- ranged to control in an on/off manner the supply of compressed air through the main duct to the outlet. The first air flow valve comprises in preferred embodiments a closure element and an actuator, in particular an electro-magnetic actuator. In a preferred embodiment, the main duct comprises two main duct parts extending essentially perpendicular to one another, wherein the closure element of first air flow control valve is arranged in the transition region between the two main duct parts for closing an air supply to the second main duct part of the main duct. This allows a simple manufacturing of the main duct and the corresponding first air flow control valve. The actuator is preferably arranged at a side wall of the main body and connected to the closure element via a shaft. In one embodiment, the closure element is held in a closing contact with a valve seat by a return spring and moved by the actuator against the force of the return spring.

According to another embodiment, the non-return valve comprises a valve ele- ment arranged axially moveable in the secondary duct. The moving direction of the non-return valve coincides with the moving direction of the second air flow control valve. Preferably, the passageway for the secondary duct is arranged at least partially in parallel to the first main duct part of the main duct allowing a simple manufacturing.

In another embodiment, the main body has an essentially straight parallelepiped housing, wherein an actuator for the first air flow control valve and the at least one inlet for the main duct are arranged at a first wall, an actuator for the second air flow control valve is arranged at a second wall, perpendicular to the first wall, and the outlet is arranged at a third wall parallel to the first wall, and wherein three remaining walls of the housing are formed as free surfaces. With such a structure, no elements or units extending to the outside of the housing are provided on the free surfaces. This allows to place several air supply units next to each other.

In one embodiment, one inlet is provided on the main body for the supplying of air via the main duct and the secondary duct, wherein the pressure of the air supplied to the secondary duct preferably is reduced using a pressure regulating valve. According to a preferred embodiment, two inlets are provided on the main body, wherein air is supplied at a first pressure from a first inlet to the outlet via the main duct and air is supplied at a second pressure from the second inlet to the outlet via the secondary duct. A common compressed air source may be provided, wherein outside the main body a pressure regulating valve is provided for reducing the pressure to be supplied via the secondary duct. The pressure of the air supplied to the secondary duct can be adjusted independently on the pressure supplied to the main duct.

In a preferred embodiment, a supply duct extending transversely through the main body is provided, wherein air is supplied to the secondary duct via this transversely extending supply duct. Several air supply units may be arranged next to one another, wherein air is supplied to the secondary ducts via the sup- ply duct. This allows a compact structure of the air supply unit and requires only a limited number of additional supply ducts at the main body.

In preferred embodiments, the air supply unit is fitted with at least one electrical connector connecting an actuator or drive unit for the first air flow control valve and/or an actuator or drive unit for the second air flow control valve with a control unit, in particular a control unit of the weaving machine.

Further advantages and features of the invention will emerge from the following description of the embodiments illustrated in the drawings. Brief Description of the Drawings

In the following, embodiments of the invention will be described in detail based on several schematic drawings in which

Fig. 1 shows a schematic cross-sectional view of an air supply unit according to a first embodiment;

Fig. 2 shows a schematic side view of the air supply unit of Fig. 1 ;

Fig. 3 shows a schematic view of a valve element of a non-return valve of the air supply unit of Figs. 1 and 2;

Fig. 4 shows a graph representing the pressure course over time at an outlet of the air supply unit;

Fig. 5 shows a front view of a number of air supply units according to the invention arranged next to one another; and Fig.6 shows a schematic cross-sectional view of an air supply unit of a second embodiment similar to Fig. 1 .

Detailed Description of Preferred Embodiments

In the following, embodiments of the invention will be described in detail with reference to the drawings. Throughout the drawings, the same or similar elements will be denoted by the same reference numerals. Fig. 1 and 2 show a first embodiment of an air supply unit 1 with a main body 2 for supplying air to a blowing device 3 (schematically shown) of an airjet weaving machine in a schematic cross-sectional view and a side view, respectively.

The main body 2 further comprises a main duct 4 with a first main duct part 5 and a second main duct part 6 for supplying air at a first pressure from the first inlet 7 to the outlet 8 and a secondary duct 9 with a first duct part 10, a second duct part 1 1 and a third duct part 12 for supplying air at a second pressure from the second inlet 13 to the outlet 8. The first inlet 7 is connectable to a first compressed air source (not shown), the second inlet 13 is connectable to a second compresses air source (not shown) and the outlet 8 is connectable to the blowing device 3 of the airjet weaving machine.

A first air flow control valve 14 is provided in the main duct 4 and is arranged to control the supply of compressed air through the main duct 4 to the outlet 8. The shown first air flow control valve 14 is a shut-off valve that is arranged to control in an on/off manner the supply of compressed air through the main duct 4. The air flow control valve 14 comprises a closure element 15 and an actuator 16, in particular an electro-magnetic actuator or any other suitable drive unit. The main duct 4 comprises two main duct parts 5 and 6 extending essentially perpendicular to one another, wherein the closure element 15 is arranged in the transition region between the two main duct parts 5 and 6 for closing the supply of air to the second main duct part 6 of the main duct 4. The actuator 16 is arranged at a side wall 35 of the main body 2 at which also the first inlet 7 is provided. The actuator 16 is connected to the closure element 15 via a shaft 17. The closure element 15 is held in a closing contact with a valve seat 19 provided at the second main duct part 6 by a return spring 18 and is moved by the actuator 16 against the force of the return spring 18.

In the secondary duct 9 a second air flow control valve 20 is provided, wherein the second air flow control valve 20 is a throttle valve and is arranged to throttle the air flow through the secondary duct 9. The secondary duct 9 ends into the main duct part 6 of the main duct 4 downstream of the first air flow control valve 14.

Further, a non-return valve 21 is provided in the secondary duct 9 downstream of the second air flow control valve 20. Fig. 3 shows in more detail the non- return valve 21 of the air supply unit 1 . The second air flow control valve 20 and the non-return valve 21 divide the secondary duct 9 in three duct parts 10, 1 1 and 12, a first duct part 10 upstream of the second air flow control valve 20, a second duct part 1 1 between the second air flow control valve 20 and the nonreturn valve 21 , and third duct part 12 downstream of the non-return valve 21 .

For a weft thread insertion a first pressure or weaving pressure is provided which is sufficiently high for allowing a reliable weft thread insertion. Appropriate first air pressures that are provided at the first inlet 7 are for example in the range of about 2 bar to about 7 bar. The second pressure or holding pressure is lower than the first pressure. Using a second pressure in the range of about 0,1 bar has been successful for reliably holding a weft thread in the blowing de- vice when not inserted. Suitable second pressures that are provided at the second inlet 13 of the air supply unit 1 are for example in the range of 1 ,5 bar.

The non-return valve 21 opens or closes due to pressure differences in the compressed air between the second main duct part 6 of the main duct 4 and the second duct part 1 1 of the secondary duct 9. No actuator is required for the non-return valve 21 .

Fig. 4 shows an example of a graph that shows the pressure over time at the outlet 8 of the air supply unit 1 . During weaving, when no weft thread is in- serted, air at the second pressure is supplied via the secondary duct 9 while the first air flow control valve 14 is closed. For a weft thread insertion, the first air flow control valve 14 is opened at an instant T1 and air at a first pressure is supplied to the outlet 8 via the main duct 4. After the weft thread insertion, the first air flow control valve 14 is closed at an instant T2. As can be seen in Fig. 4, a fast transition between the two pressure levels is achieved. The non-return valve 21 is closed at an instant T3, shortly after the first air flow control valve 14 has been opened. After the first air flow control valve 14 is closed again, the non-return valve 21 is opened again at an instant T4. The function of the air supply unit 1 will be explained with reference to Figs. 1 to 4. When closing the first air flow control valve 14, the pressure in the second main duct part 6 of the main duct 4 downstream of the first air flow control valve 14 will drop. The pressure in the third duct part 12 of the secondary duct 9 is substantially equal to the pressure in the second main duct part 6. When the pressure in this third duct part 12 of the secondary duct 9 is below a pressure in the second duct part 1 1 of the secondary duct 9 upstream of the non-return valve 21 , the non-return valve 21 opens and air can be supplied at the second pressure to the outlet 8. As long as no air flows through the opened second air flow control valve 20, the pressure upstream and downstream of the second air flow control valve 20 is essentially the same. Therefore, a pressure that is provided at the second inlet 13 will act via the second duct part 1 1 on the non-return valve 21 for opening the non-return valve 21 . This pressure is higher than when an air stream is throttled by the second air flow control valve 20 after the non-return valve 21 has opened and air flows through the second air flow control valve 20. For ex- ample, the pressure supplied via the second inlet 13 and prevailing in static conditions, i.e. before the opening of the non-return valve 21 , may be chosen to 1 ,5 bar, whereas the pressure supplied via the secondary duct 9 after the nonreturn valve 21 has opened due to the throttling drops to 0,1 bar. This way on one hand after closing the first air flow control valve 14 a fast opening of the non-return valve 21 is achieved and on the other hand after the opening of the first air flow control valve 14 a fast closing of the non-return valve 21 is achieved.

Further, by providing the non-return valve 21 downstream of the second air flow control valve 20 in the secondary duct 9 of the main body 2, a compact structure of the air supply unit 1 is given, wherein an air volume between the nonreturn valve 21 and the second air flow control valve 20 and between the nonreturn valve 21 and the first air flow control valve 14 is kept small. This allows prevailing pressures upstream and/or downstream of the non-return valve 21 to quickly adapt to changes in the conditions due to an opening or closure of the first air flow control valve 14 and the non-return valve 21 . In particularly a fast decreasing of the pressure in the second main duct part 6 of the main duct 4 and in the third main duct part 12 of the secondary duct 9 is achieved after the closing of the first air flow control valve 14. This allows to define precisely the moment at which a weft thread during a weft thread insertion is no longer propelled by a blowing device 3 receiving air from an air supply unit 1 according to the invention. This way e.g. a braking and/or a clamping of the weft thread at the end of the weft thread insertion may be done without a risk of damaging the weft thread because of the blowing device 3 blows too hard.

Due to the higher pressure acting on the non-return valve 21 under static conditions and the small volumes of the duct parts 1 1 and 12 of the secondary duct 9 downstream of the second air flow control valve 20, the non-return valve 21 opens or closes quickly in response to a closing or opening of the first air flow control valve 14 for a fast and reliable transition from an air supply at a first pressure to an air supply at a second pressure and vice versa. In addition, pressure drops at the outlet 8 to a pressure below the expected holding pressure are successfully avoided.

The main duct parts 5, 6 and the duct part 10 are implemented as bore-holes in the main body 2 which allows a simple manufacturing. The duct part 10 of the secondary duct 9 is essentially in parallel to the first main duct part 5 of the main duct 4. The non-return valve 21 is placed in the passageway 22 of which the duct part 10 makes part. In the shown embodiment, the non-return valve 21 comprises two sleeve-type elements 23, 24 with a central through-opening 48, 49 and a valve element 25 of the non-return valve 21 arranged slidingly in the sleeve-type elements 23, 24. The valve element 25 is preferably executed as light as possible in order to allow a fast movement. The central though- opening 48 of the sleeve-type element 23 forms the duct part 1 1 , while the central through-opening 49 of the sleeve-type element 24 forms the duct part 12. The two sleeve-type elements 23, 24 are fixedly secured to each other and sealingly arranged in the passageway 22. Further, a fastening element 26 is provided for fastening the sleeve-type elements 23, 24 in the passageway 22 that for example comprises a screw element. The sleeve-type elements 23, 24 may easily be replaced. The passageway 22 is dimensioned sufficiently large for allowing a simple manufacturing of the main body 2. The diameter of the central through-openings 48, 49 of the two sleeve-type elements 23, 24, which central through-openings 48, 49 form the duct parts 1 1 and 12 respectively, is chosen substantially smaller than the diameter of the passageway 22 for minimizing the air volume in the second and third duct part 1 1 and 12 of the secon- dary duct 9. In order to achieve an airtight closure by the non-return valve 21 , the non-return valve 21 comprises a closure ring 51 . The closure ring 51 is arranged between the sleeve-type elements 23 and 24.

The second air flow control valve 20 comprises a stationary valve seat 27 with an essentially circular-cylindrical inside surface and a plunger 28 with a conical outer surface. The conicity of the plunger 28 preferably is between 3 ° and 30 °. In the embodiment shown, the valve seat 27 is formed at the entry region 47 of the central through-opening 48 of the duct part 1 1 that is part of the sleeve-type element 23. To close the second air flow control valve 20 airtight, the plunger 28 comprises a closure ring 52 which can cooperate with the recess 53 of the sleeve-type element 23. Further the plunger 28 comprises a plunger skirt 43 which can be moved to contact the surface 54 of the sleeve-type element 23. This contact allows to perform an unambiguous positioning of the plunger 28 so that a controlling of the actuator 29 of the second air flow control valve 20 may be done precisely. In this case the closure ring 52 is pressed into the recess 53. The position of the plunger 28 is adjustable with respect to the valve seat 27 for adjusting a throttling gap. For this purpose, the second air flow control valve 21 comprises an actuator 29, in particular a stepper motor or any other suitable drive unit. The actuator 29 is coupled with a screw-thread device for transforming a rotational movement of the actuator 29 into an axial movement of the plunger 28. The second air flow control valve 20 can be set to a desired throttling for throttling suitable and adapted to the weaving conditions the air flow through the second duct 9. The plunger 28 is arranged at a slider element 30 and can be moved with the slider element 30 in the axial direction of the passageway 22.

As schematically shown in Fig. 2, the air supply unit 1 is further fitted with at least one electrical connector 31 , 32 connecting the actuator 16 for the first air flow control valve 14 and connecting the actuator 29 for the second air flow control valve 20 with a control unit 33, in particular a control unit of the weaving machine.

The main body 2 has an essentially straight parallelepiped housing 34, wherein the actuator 16 for the first air flow control valve 14 and the first inlet 7 are arranged at a first wall 35, the actuator 29 for the second air flow control valve 20 is arranged at a second wall 36, perpendicular to the first wall 35, and the outlet 8 is arranged at a third wall 37 parallel to the first wall 35, and the remaining three walls 38, 39, 40 of the housing 34 are formed as free surfaces, as schematically shown in Fig. 5. With such a structure, no elements or units extending to the outside of the housing 34 are provided on the free surfaces. This allows placing several air supply units 1 next to each other.

As shown in Figs. 1 , 2 and 5 a supply duct 41 (shown in broken lies) extending transversely through the main body 2 is provided, wherein the first duct part 10 of the secondary duct 9 coincides with the supply duct 41 and air is supplied to the secondary duct 9 via the supply duct 41 . When arranging several air supply units 1 next to one another, for example as shown in Fig. 5, the supply ducts 41 of a number of air supply units 1 are coupled and air is supplied to the secon- dary ducts 9 via the supply ducts 41 . In this case the second inlet 13 is located near the supply duct 41 of a first air supply unit 1 that is arranged at one side and the supply duct 41 of an last air supply unit 1 that is arranged at the opposite side is sealed with a cover 50. This allows a compact structure of the air supply unit 1 with a limited number of additional air ducts at the main body 2. As shown in Fig. 5 compresses air can be supplied to the air supply unit 1 according to the invention via several air ducts 55 and air ducts (not shown) to an inlet 7. In the embodiment shown in Figs. 1 and 3, the plunger 28 comprises a plunger head 42 and a plunger skirt 43 and the second air flow control valve 20 comprises a support structure 44 arranged in the passageway 22 for the secondary duct 9, wherein the plunger 28 is slideably supported in the support structure 44. The non-return valve 21 , the second air flow control valve 20, the support structure 44 and the actuator 29 for the second air flow valve 20 are inserted in the passageway 22. With a sealing ring 45 as shown in Fig. 1 , the support structure 44 is sealingly arranged in the passageway 22 in order to avoid air losses. The support structure 44 allows to dimension the diameter of the plunger 28 smaller than the diameter of the passageway 22. The sliding ele- ment 30 of the plunger 28 is also sealingly arranged with a sealing ring 46 in the support structure 44. Due to the small diameter of the sealing ring 46 also the force required for moving the plunger 28 is minimized, for example against the force of a pressure prevailing in the first duct part 10 of the second duct 9. Fig. 6 is a schematic cross-sectional view of an air supply unit 1 according to a second embodiment of the invention. In the embodiment shown in Fig. 6, the plunger 28 is formed as an integral unit slidingly arranged in the passageway

22, wherein the plunger 28 is guided by the sidewalls of the passageway 22. Also a closure ring 56 is provided between the plunger 28 and the actuator 29. In this embodiment, the first duct part 1 1 of the secondary duct 9 is vanishingly small. The plunger 28 can co-operate with a valve seat 27 that is provided at the entry region 47 of the central through-opening of the sleeve-type element

23, more particularly the entry region 47 downstream of the valve seat 27 of the second air flow control valve 21 . In this case the first inlet 7 and the second inlet 13 are arranged next to one another at the wall 35. Each inlet 7 and each inlet 13 can be connected via an own air duct to a compressed air source. An air supply unit and a method according to the invention are obviously not limited to the exemplary embodiments which have been illustrated and described, but can also include variations and combinations thereof which fall under the claims. An air supply unit according to one of the claims is particularly suitable for applying a method according to one of the claims.

Claims

An air supply unit for supplying air to a blowing device (3) of an airjet weaving machine, wherein the air supply unit (1 ) comprises a main body (2), the main body (2) comprises at least one inlet (7, 13) for air, an outlet (8) for air, a main duct (4) for supplying air at a first pressure from an inlet (7) to the outlet (8), a secondary duct (9) for supplying air at a second pressure from an inlet (13) to the outlet (8), with a first air flow control valve (14) provided in the main duct (4) and arranged to control the supply of compressed air through the main duct (4) to the outlet (8), and with a second air flow control valve (20) provided in the secondary duct (9), wherein the second air flow control valve (20) is a throttle valve and arranged to throttle the air in the secondary duct (9), and wherein the secondary duct (9) ends into the main duct (4) downstream of the first air flow control valve (14), characterized in that a non-return valve (21 ) is provided in the secondary duct (9) downstream of the second air flow control valve (20).

The air supply unit according to claim 1 , characterized in that an essen¬ tially linear passageway (22) is provided in the main body (2) for the formation of the secondary duct (9), wherein the second air flow control valve (20) and the non-return valve (21 ) are arranged in line in the passageway (22).

The air supply unit according to claim 1 or 2, characterized in that sleeve-type elements (23, 24) with a central through-opening (48, 49) are provided in a passageway (22) of the main body (2), wherein the nonreturn valve (21 ) is arranged between the sleeve-type elements (23, 24) and wherein a valve seat (27) of the second air flow control valve (20) is provided at the entry region (47) of central through-opening (48) at the sleeve-type element (23) arranged upstream of the other sleeve-type element (24).

The air supply unit according to claim 3, characterized in that the sleeve- type element (23, 24) is fixedly secured in the passageway (22) of the main body (2), in particular using a fastening element (26).

5. The air supply unit according to any one of claims 1 to 4, characterized in that the second air flow control valve (20) comprises a stationary valve seat (27) with an essentially circular-cylindrical inside surface and a plunger (28) with a conical outer surface.

6. The air supply unit according any one of claims 1 to 5, characterized in that the second air flow control valve (20) comprises an actuator (29) for adjusting the throttling gap, in particular an electrically controlled actua- tor.

7. The air supply unit according to claim 5 or 6, characterized in that the second air flow control valve (20) comprises a support structure (44) sealingly arranged in the secondary duct (9), wherein the plunger (28) is slideably supported in the support structure (44).

8. The air supply unit according to claim 7, characterized in that a diameter of the plunger (28) is smaller than a cross-section of the second duct part (1 1 ) of the secondary duct (9) upstream of the valve seat (27) of the sec- ond air flow control valve (20).

9. The air supply unit according to any of claims 1 to 8, characterized in that the first air flow control valve (14) comprises a closure element (15) and an actuator (16), in particular an electro-magnetic actuator, arranged to control in an on/off manner the supply of compressed air through the main duct (4) to the outlet (8).

10. The air supply unit according to any one of claims 1 to 9, characterized in that the non-return valve (21 ) comprises a slider element (25) arranged axially moveable in the secondary duct (9).

1 1 . The air supply unit according to any one of claims 1 to 10, characterized in that the main body (2) has an essentially straight parallelepiped housing (34), wherein an actuator (16) for the first air flow control valve (14) and an inlet (7) for the main duct (4) are arranged at a first wall (35), an actuator (29) for the second air flow control valve (20) is arranged at a second wall (36), perpendicular to the first wall (35), and the outlet (8) is arranged at a third wall (37) parallel to the first wall (35), and wherein three remaining walls (38, 39, 40) of the housing (34) are formed as free surfaces.

The air supply unit according to any one of claims 1 to 1 1 , characterized in that two inlets (7, 13) are provided on the main body (2), wherein air is supplied at a first pressure from a first inlet (7) to the outlet (8) via the main duct (4) and air is supplied at a second pressure from the second inlet (13) to the outlet (8) via the secondary duct (9).

The air supply unit according to claim 12, characterized in that a supply duct (41 ) extending transversely through the main body (2) is provided, wherein air is supplied to the secondary duct (9) via this supply duct (41 ) extending transversely.

The air supply unit according to any one of claims 1 to 13, characterized in that the non-return valve (21 ) is arranged in the secondary duct (9) near to the place where the secondary duct (9) ends into the main duct (4).

Method for applying an air supply unit (1 ) for supplying air to a blowing device (3) of an airjet weaving machine for inserting a weft thread, wherein the air supply unit (1 ) comprises a main body (2), the main body (2) comprises at least one inlet (7, 13) for air, an outlet (8) for air, a main duct (4) for supplying air at a first pressure from an inlet (7) to the outlet (8), a secondary duct (9) for supplying air at a second pressure from an inlet (13) to the outlet (8), wherein the air supply unit (1 ) further comprises a first air flow control valve (14) provided in the main duct (4) and arranged to control the supply of compressed air through the main duct (4) to the outlet (8) and comprises a second air flow control valve (20) provided in the secondary duct (9), wherein the second air flow control valve (20) is a throttle valve and arranged to throttle the air in the secondary duct (9), wherein the secondary duct (9) ends into the main duct (4) downstream of the first air flow control valve (14), and wherein a nonreturn valve (21 ) is provided in the secondary duct (9) downstream of the second air flow control valve (20), wherein the method comprises the steps of: supplying air at a second pressure via the secondary duct (9) while the first air flow control valve (14) is closed, opening the first control valve (14) and supplying air at a first pressure via the main duct (4) for a weft thread insertion of a weft thread, wherein the first pressure is higher than the second pressure, and subsequently closing the first air flow control valve (14).